A systematic study on copper (II)-alginate beads as catalysts for the synthesis of biodiesel via esterification of oleic acid and methanol is here reported for the first time. The chemical structure and morphologies of these catalysts were fully characterized by XRD, FT-IR, and SEM. The copper (II)-alginate beads showed a tubular structure with entangled reticulation. In the presence of copper (II)-alginate catalyst, the biodiesel conversion of 71.8% was achieved from oleic acid with methanol under the most mild conditions (1/10 oleic acid to methanol molar ratio, 250 mg catalyst, 70°C for 3 h), optimized by single-factor experiments. The catalyst could be easily separated from the reaction mixture and stabilized for a certain time. This material can also catalyze other esterification of fatty acids with different carbon chain lengths, as well as the pretreatment of non-edible oils with high acid value. Our findings showed that the copper (II)-alginate is a suitable catalyst for esterification and would provide more choices for industrial application in the future.
Keywords: biodiesel; esterification; heterogeneous acid; sodium alginate.